This invention relates to internal combustion engines of the four cycle reciprocating type wherein a first down stroke of a piston effects intake of working fluid following the preceding exhaust, followed by a first up stroke of the piston that effects compression of said working fluid, followed by a second down stroke of the piston as a result of combustion and expansion of the working fluid, and finally followed by a second up stroke of the piston that effects exhaust and expanding of said working fluid.
Poppet valves are highly developed and used for opening and closing head ports for the intake and exhaust of working fluid, it being customary to open and close valves in advance of top-dead-center and bottom-dead-center positions of the crank shaft, and to have so-called valve overlap during which the exhaust valve remains open while the intake valve is opened. Combustion chamber shape is critical in relation to the positions of said valves and shape of the piston head, and there are problems with scavenging the exhaust gases by means of displacement with intake gases. The engine design configurations become more critical with high performance engines operating at high speeds of rotation, carburetion and/or fuel injection together with filling the cylinder on the intake stroke becoming a limiting factor. That is, suction of the downward moving piston cannot draw in a full measure of fuel-air mixture through the intake port in the head that covers the cylinder. Accordingly, it is an object of this invention to provide cylinder charging means by which the cylinder is opened to additional air and/or a carbureted mixture thereof.
The down stroke of the piston during the intake cycle creates a partial vacuum in the cylinder, and normally sucks air and/or carbureted mixture into and partially fills the cylinder; that is, to an extent that time permits outside pressure to force the air-fuel mixture to enter therein. Fluid dynamics prevents complete filling to atmospheric pressure, and in order to achieve best results the intake valve is opened substantially before top-dead-center position and is closed substantially after bottom-dead-center position (of the crank and piston). It becomes apparent therefore that the lower portion of the intake stroke is characterized by an open cylinder, permitting the in rush inertia of gases to fill the cylinder as much as possible prior to closing the intake valve for the compression stroke. Thus, the actual compression of gases does not commence until the piston is well on its excursion in the up stroke, in practice approximately midway therealong. Accordingly, it is another object of this invention to open the cylinder to additional charging throughout the lower portion of the intake and compression strokes of the piston, to additionally charge the cylinder with air and/or carbureted mixture. In practice, the lower portion of the cylinder chamber is ported laterally to an air intake stack and carburetion or fuel injection.
Engines of the type under consideration are highly developed, and accordingly it is still another object of this invention to utilize such engines substantially without change, adding thereto the features of the present invention which greatly improved performance. As shown, the cylinder charging means is adapted to the induction side of the engine cylinder and head combination, adding an intake stack in open communication with the lower portion of the cylinder chamber and characterized by a carburetor protected by valve means, preferably a check valve that permits induction only.